Illumination system to eliminate laser speckle and projection system employing the same

ABSTRACT

An illumination system designed to remove laser speckle and a projection system including the same. The illumination system includes a laser light source having at least one laser, a diffractive optical element to divide a laser beam emitted from the laser light source into a plurality of sub-beams and to periodically move in such a way as to temporally average the speckle of the laser beam, and an optical fiber bundle including a plurality of fibers with the same length to divide the sub-beams into smaller sub-beams. The illumination system divides the laser beam emitted from the laser light source into sub-beams and temporally or spatially averages the sub-beams, thereby effectively reducing or removing laser speckle. The projection system employing the illumination system can provide improved image quality.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119 of KoreanPatent Application No. 10-2004-106536, filed on Dec. 15, 2004, in theKorean Intellectual Property Office, the disclosure of which isincorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present general inventive concept relates to an illuminating systemdesigned to eliminate speckle produced by laser light and a projectionsystem employing the same, and more particularly, to an illuminationsystem designed to effectively reduce or eliminate laser speckle bydividing a beam emitted from a laser light source into sub-beams andtemporally or spatially averaging the sub-beams and a projection systememploying the same.

2. Description of the Related Art

A projection system using a laser light source provides a wide range ofcolor rendition due to a wide color gamut while achieving high opticalefficiency due to superior collimation. However, the laser-basedprojection system suffers from speckle due to a coherence of a laserbeam. The speckle results from interference among randomly phasedcoherent beams reflected from a rough surface. The speckle is a mainfactor degrading resolution and quality of an image.

FIG. 1 illustrates a conventional illuminating device designed toeliminate laser speckle, as disclosed in U.S. Pat. No. 6,249,381.Referring to FIG. 1, in the conventional illuminating device, laserlight emitted by a laser light source 10 is incident on a lens 11. Then,the laser light is condensed by the lens 11 and is incident on anincident end of an optical fiber bundle 12. The laser light is emittedthrough the optical fiber bundle 12 and an optical fiber 13 andilluminates a spatial modulator 15 that is a transmissive liquid crystaldisplay through a lens 14. The conventional illuminating device furtherincludes a projection lens 16 and a screen 17 to form an image thereon.

Since the optical fiber bundle 12 consists of a plurality of opticalfibers with different lengths, a beam passing through each fiber has adifferent optical path length, thus contributing to a reduction incoherency of the beam.

However, since the beams passing through the optical fiber bundle 12have different phases, the efficiency of speckle removal is degraded.Furthermore, the optical fiber bundle 12 having the optical fibers withdifferent lengths is complicated to manufacture.

SUMMARY OF THE INVENTION

The present general inventive concept provides a slim and compactillumination system that can effectively reduce or eliminate laserspeckle by spatially averaging a laser beam using a diffractive opticalelement or temporally averaging a laser beam using a reflectivevibrator, and a projection system employing the same.

Additional aspects of the present general inventive concept will be setforth in part in the description which follows and, in part, will beobvious from the description, or may be learned by practice of thegeneral inventive concept.

The foregoing and/or other aspects of the present general inventiveconcept may be achieved by providing an illumination system to removespeckle of a laser beam, the illumination system including a laser lightsource having at least one laser to emit a laser beam, a diffractiveoptical element to divide the laser beam emitted from the laser lightsource into a plurality of first sub-beams and to periodically move totemporally average the speckle of the laser beam, and an optical fiberbundle including a plurality of fibers with the same length to dividethe first sub-beams into smaller second sub-beams.

Each of the plurality of first sub-beams may include a plurality ofbeamlets that are focused in an overlaying fashion on one another. Thediffractive optical element may be rotatable.

The foregoing and/or other aspects of the present general inventiveconcept may also be achieved by providing an illumination system toremove speckle of a laser beam, the illumination system including alaser light source having at least one laser to emit a laser beam, anoptical fiber bundle including a plurality of fibers with the samelength to divide the laser beam emitted from the laser light source intoa plurality of sub-beams, and a vibrator to vibrate to temporallyaverage the plurality of sub-beams.

The vibrator may include a reflecting mirror and a piezoelectric elementto vibrate the reflecting mirror.

The illumination system may further include a beam-shaping unit locatedafter the optical fiber bundle along a path of the laser beam to converta cross-section of each of the plurality of sub-beams into apredetermined shape of a display device. The beam-shaping unit may be alight pipe. The beam-shaping unit may include a collimating lens andfirst and second fly-eye lens arrays or a collimating lens and abeam-shaping diffractive optical element having a diffractive pattern.

The foregoing and/or other aspects of the present general inventiveconcept may also be achieved by providing an illumination system,including a laser light source unit to emit a laser beam, a movabletemporal averaging unit to temporally average the laser beam emittedfrom the laser light source unit, and an optical fiber bundle having aplurality of optical fibers each having the same length to divide thelaser beam emitted from the laser light source unit into a plurality ofsub-beams.

The foregoing and/or other aspects of the present general inventiveconcept may also be achieved by providing an illumination system,including a laser light source to emit a laser beam, a first averagingunit to average the laser beam, an optical bundle to divide the laserbeam averaged by the first averaging unit into sub-beams, and a secondaveraging unit to average the sub-beams.

The foregoing and/or other aspects of the present general inventiveconcept may also be achieved by providing a projection system to removespeckle of a laser beam, the projection system including a laser lightsource having at least one laser to emit a laser beam, a diffractiveoptical element to divide the laser beam emitted from the laser lightsource into a plurality of first sub-beams and to periodically move totemporally average the speckle of the laser beam, an optical fiberbundle including a plurality of fibers with the same length to dividethe sub-beams into smaller second sub-beams, a beam-shaping unit toshape the second sub-beams output from the optical fiber bundle, adisplay device to produce an image using the second-sub beams shaped bythe beam shaping unit, a screen, and a projection lens unit to enlargeand project the image onto the screen.

The foregoing and/or other aspects of the present general inventiveconcept may also be achieved by providing a projection system to removespeckle of a laser beam, the projection system including a laser lightsource having at least one laser to emit a laser beam, an optical fiberbundle including a plurality of fibers with the same length to dividethe laser beam emitted from the laser light source into a plurality ofsub-beams, a beam-shaping unit to shape the plurality of sub-beamspassing through the optical fiber bundle, a vibrator to vibrate totemporally average the plurality of sub-beams, a display device toproduce an image using the plurality of sub-beams temporally averaged bythe vibrator, a screen, and a projection lens unit to enlarge andproject the image onto the screen.

The foregoing and/or other aspects of the present general inventiveconcept may also be achieved by providing an image projection system,including a laser light source to emit a laser beam, a first averagingunit to average the laser beam, an optical bundle to divide the laserbeam averaged by the first averaging unit into sub-beams, a secondaveraging unit to average the sub-beams, and a display device to formand display an image using the sub-beams.

The foregoing and/or other aspects of the present general inventiveconcept may also be achieved by providing an image projection system,including a laser light source to emit a laser beam, an optical fiberbundle having a plurality of optical fibers to divide the laser beaminto first sub-beams, a collimating lens to collimate the firstsub-beams, a first fly-lens array to divide the collimated firstsub-beams into second sub-beams, a second fly-lens array to focus thesecond sub-beams to overlap with each other and to provide a beam of apredetermined shape, an averaging unit to temporally average the beam ofthe predetermined shape, and a display device to form and display animage using the temporally averaged beam of the predetermined shape.

The foregoing and/or other aspects of the present general inventiveconcept may also be achieved by providing an image projection system,comprising: a laser light source to emit a laser beam, an optical fiberbundle having a plurality of optical fibers to divide the laser beaminto sub-beams, a collimating lens to collimate the sub-beams, abeam-shaping diffractive optical element having a predetermineddiffractive pattern to shape a cross-section of the sub-beams, anaveraging unit to temporally average the sub-beams shaped by thebeam-shaping diffractive optical element, and a display device to formand display an image using the temporally averaged sub-beams.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects of the present general inventive concept willbecome apparent and more readily appreciated from the followingdescription of the embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 illustrates a conventional illuminating device;

FIG. 2 schematically illustrates a projection system including anillumination system according to an embodiment of the present generalinventive concept;

FIG. 3 illustrates profiles of sub-beams produced by a diffractiveoptical element of the projection system of FIG. 2;

FIG. 4A illustrates a view of a section A-A of an optical fiber bundleof FIG. 2;

FIG. 4B illustrates a view of a section B-B of the optical fiber bundleof FIG. 2;

FIGS. 5 and 6 illustrate modified examples of the projection system ofFIG. 2 according to various embodiments of the present general inventiveconcept;

FIG. 7 schematically illustrates a projection system including anillumination system according to another embodiment of the presentgeneral inventive concept;

FIG. 8 schematically illustrates a configuration of a reflectivevibrator of the illumination system of FIG. 7; and

FIGS. 9 and 10 illustrate modified examples of the projection system ofFIG. 7. according to various embodiments of the present generalinventive concept.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentgeneral inventive concept, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to the likeelements throughout. The embodiments are described below in order toexplain the present general inventive concept while referring to thefigures.

FIG. 2 illustrates a projection system to eliminate laser speckleaccording to an embodiment of the present general inventive concept.Referring to FIG. 2, the projection system includes a laser light source50, a diffractive optical element (DOE) 52 to remove the speckle of alaser beam emitted by the laser light source 50, an optical fiber bundle54 to divide the laser beam passing through the DOE 52 into sub-beams, abeam-shaping unit 56 to shape the sub-beams, and a display device 62 toproduce an image from the sub-beams shaped by the shaping unit 56.

The projection system can further include a condensing lens 58 that isdisposed in an optical path between the beam-shaping unit 56 and thedisplay device 62 to condense the sub-beams, a projection lens unit 64to enlarge and project the image produced by the display device 62 ontoa screen 66, and a light path changer 60 (e.g., a reflecting mirror)that is disposed in the optical path between the condensing lens 58 andthe display device 62 to change a propagation path of the condensedsub-beams such that the condensed sub-beams are directed toward thedisplay device 62.

The laser light source 50 can include a plurality of lasers to emitlaser beams with different wavelengths. Each laser may be one of a solidstate laser, a semiconductor laser, and a gas laser.

The DOE 52 periodically moves or rotates in such a way as to temporallyaverage laser beams emitted from the laser light source 50, therebyeffectively removing laser speckle. FIG. 3 illustrates the DOE 52 ofFIG. 2. Referring to FIGS. 2 and 3, the DOE 52 includes a plurality ofunit cells 52 a. Each of the plurality of unit cells 52 a has apredetermined shape, such as circular or various other shapes. The laserbeam emitted from the laser light source 50 is divided into a pluralityof sub-beams 53 with different phases and optical paths as the laserbeam passes through the plurality of unit cells 52 a. Each of theplurality of sub-beams 53 includes multiple beamlets 53 a focused in anoverlaying fashion on one another in such a way as to spatially averagethe laser beam. Furthermore, the DOE 52 can be rotated by a motor M insuch a way as to temporally average the laser beam, thereby eliminatingthe laser speckle effectively.

FIGS. 4A and 4B illustrate the optical fiber bundle 54 taken along aline A-A of FIG. 2 and taken along a line B-B of FIG. 2, respectively.Referring to FIGS. 2-4B, the optical fiber bundle 54 includes aplurality of optical fibers 54 a with the same length to further dividethe sub-beams 53 produced by the DOE 52 into smaller sub-beams.Accordingly, the optical fiber bundle 54 and the DOE 52 spatiallyaverage the laser beam in order to eliminate coherence of the laserbeam.

When a contrast of the laser speckle is less than 4%, the laser specklecannot be detected by a naked eye. The contrast of the laser speckle isdefined by Equation (1):

$\begin{matrix}{C = {\frac{\sqrt{\left\langle I_{i}^{2} \right\rangle - \left\langle I_{i} \right\rangle^{2}}}{\left\langle I_{i} \right\rangle} = {\frac{\sigma}{\mu} \times 100\mspace{14mu}(\%)}}} & (1)\end{matrix}$

where I_(i) is an average intensity of a laser beam passing through ani-th unit cell 52 a of the DOE 52, a denotes σ standard deviation ofintensity values, and μ is a mean intensity value.

A laser beam with a Gaussian distribution (Gaussian beam) emitted by thelaser light source 50 is converted to a beam with a uniform intensitydistribution as it passes through the DOE 52. That is, the DOE 52 splitsthe Gaussian beam into the plurality of sub-beams 53 that are thenfocused in an overlapping fashion and converted into the beam with theuniform intensity distribution. The optical fiber bundle 54 subsequentlyfurther divides the sub-beams 53 into the smaller sub-beams, thusincreasing the uniformity of the laser beam.

The beam-shaping unit 56 then shapes a cross-section of the laser beamto match a shape of the display device 62. The display device 62 may bea transmissive liquid crystal display (LCD), a Liquid Crystal on Silicon(LCoS) display, a Deformable Micromirror Device (DMD), a Grating LightValve (GLV), or the like. The display device 62 may have a rectangularshape with an aspect ratio of 4:3 or 16:9. To achieve high opticalefficiency, the beam having a circular cross-section emitted by thelaser light source 50 can be shaped to match the rectangular shape ofthe display device 62. For example, the beam-shaping unit 56 may be alight pipe. A beam incident on the light pipe has a uniform intensitydistribution and is shaped to match the cross-section of the light pipeas it is totally reflected within the light pipe. The light pipe canhave a rectangular cross-section with an aspect ratio of 4:3 or 16:9,similar to the display device 62.

The condensing lens 58 focuses the beam shaped by the beam-shaping unit56 onto the display device 62. The light path changer 60, such as thereflecting mirror, is disposed in the optical path between thecondensing lens 58 and the display device 62 and changes the propagationpath of the laser beam. Since the light path changer 60 may be usedusefully to allow effective installation of optical components in theprojection system, thus providing a slim and compact projection system,a plurality of light path changers 60 may be arranged if necessary.

The beam shaped by the beam-shaping unit 56 is incident onto the displaydevice 62, and the image produced by the display device 62 is enlargedand projected onto the screen 66 by the projection lens unit 64.

The laser light source 50 can include the plurality of lasers tosequentially emit color beams with different wavelengths. For example,the laser light source 50 may include first, second, and third lasers torespectively emit red (R), green (G), and blue (B) beams. Imagescorresponding to the R, G, and B beams are sequentially produced andprojected onto the screen 66 in order to produce a color image.

FIG. 5 illustrates a projection system having a modified beam-shapingunit 56′ according to an embodiment of the present general inventiveconcept. The projection system of FIG. 5 has the same construction asthe projection system of FIG. 2 except for the beam-shaping unit 56′.Referring to FIG. 5, the beam-shaping unit 56′ includes a collimatinglens 68 to collimate an incident beam into a parallel beam and first andsecond fly-eye lens arrays 69 a and 69 b.

A beam emitted from the optical fiber bundle 54 is collimated into theparallel beam by the collimating lens 68, and is then incident on thefirst fly-eye lens array 69 a. The incident beam is divided into aplurality of sub-beams by unit cells of the first fly-lens array 69 a,which are then focused onto corresponding unit cells of the secondfly-lens array 69 b. The second fly-lens array 69 b focuses thesub-beams from the first fly-lens array 69 a in an overlaying fashion toprovide a uniform shaped beam.

The beam shaped by the beam-shaping unit 56′ is focused onto the displaydevice 62 by the condensing lens 58. The image created by the displaydevice 62 is enlarged and projected onto the screen 66 by the projectionlens unit 64.

FIG. 6 illustrates projection system similar to the projection system ofFIG. 2 having a modified beam-shaping unit 56″ according to anotherembodiment of the present general inventive concept. The projectionsystem of FIG. 6 has a similar construction as the projection system ofFIG. 2 except for the beam-shaping unit 56″. Furthermore, the projectionsystem of FIG. 6 does not include a condensing lens between thebeam-shaping unit 56″ and the light path changer 60. Referring to FIG.6, the beam-shaping unit 56″ includes a collimating lens 70 to collimatean incident beam into a parallel beam and a beam-shaping DOE 71to shapethe parallel beam. The beam-shaping DOE 71 shapes the cross-section of abeam emitted from a laser light source 50 to match the shape of thedisplay device 62. Furthermore, a diffractive pattern of thebeam-shaping DOE 71 may be used to control a divergence angle of thebeam. The diffractive pattern of the beam-shaping DOE 71 can be used tospatially average the parallel beam. By controlling the divergence angleof the beam in such a way as to increase an F-number of an illuminationsystem, a slim and compact projection system can be provided.

The beam shaped by the beam-shaping DOE 71 is incident onto the displaydevice 62, and the image produced by the display device 62 is enlargedand projected onto the screen 66 by the projection lens unit 64.

As illustrated in FIG. 2, an illumination system according to andembodiment of the present general inventive concept includes the laserlight source 50 having the plurality of lasers to emit the beams ofdifferent wavelengths, the DOE 52 to divide the laser beam emitted bythe laser light source 50 into the sub-beams 53, the optical fiberbundle 54 to divide the sub-beams 53 into the smaller sub-beams, and thebeam-shaping unit 56 to shape the smaller sub-beams to match the shapeof the display device 62 to produce the image.

The beam-shaping unit 56 may be configured in various ways to convertthe cross-section of the laser beam emitted from the laser light source50 into a rectangular shape of the display device 62. For example, whileFIG. 2 illustrates the beam-shaping unit 56 as the light pipe, FIG. 5illustrates the beam-shaping unit 56′ including the collimating lens 68and the first and second fly-eye lens arrays 69 a and 69 b as, and FIG.6 illustrates the beam-shaping unit 56″ including the collimating lens70 and the beam-shaping DOE 71.

The illumination system as described above and the projection systememploying the same use the rotating DOE 52 to temporally and spatiallyaverage a laser beam and the optical fiber bundle 54 to furtherspatially average the laser beam, thereby effectively removing laserspeckle from the laser beam.

FIG. 7 schematically illustrates a projection system according toanother embodiment of the present general inventive concept, and FIGS. 9and 10 show modified examples of the projection system of FIG. 7according to various embodiments of the present general inventiveconcept.

Referring to FIG. 7, the projection system includes a laser light source80, an optical fiber bundle 82 to divide a beam emitted from the laserlight source 50 into sub-beams, a beam-shaping unit 86 to shape thesub-beams, a vibrator 90 to vibrate the sub-beams shaped by thebeam-shaping unit 86 in order to remove laser speckle therefrom, and adisplay device 92 to produce an image using the sub-beams vibrated bythe vibrator 90.

The projection system can further include a first condensing lens 84disposed in an optical path between the optical fiber bundle 82 and thebeam-shaping unit 86, a second condensing lens 88 disposed between thebeam-shaping unit 86 and the vibrator 90, and a projection lens unit 94to enlarge and project the image produced by the display device 92 ontoa screen 96.

The laser light source 80 sequentially emits laser beams with differentwavelengths. The optical fiber bundle 82 includes a plurality of opticalfibers with the same length and performs substantially the sameoperations as described with reference to the optical fiber bundle 54illustrated of FIGS. 4A and 4B. The laser beam emitted from the laserlight source 80 is divided into the sub-beams by the optical fiberbundle 82, and the sub-beams are then focused into the beam-shaping unit86 by the first condensing lens 84.

The beam-shaping unit 86 converts a cross-section of the beam emittedfrom the laser light source 80 into a shape of the display device 92.For example, the beam-shaping unit 86 may be a light pipe as illustratedin FIG. 7. Alternatively, the beam-shaping unit 86 may include acollimating lens 101 and first and second fly-eye lens arrays 102 a and102 b as illustrated in FIG. 9, or the beam-shaping unit may include acollimating lens 104 and a beam-shaping DOE 105 having a diffractivepattern as illustrated in FIG. 10. As opposed to the projection systemof FIG. 7, the projection system illustrated in FIG. 9 may not includethe first condensing lens 84 between the optical fiber bundle 82 and thebeam-shaping unit 86. The projection system illustrated in FIG. 10 maynot include the first condensing lens 84 between the optical fiberbundle 82 and the beam-shaping unit and the second condensing lens 88between the beam-shaping unit 86 and the vibrator 90.

FIG. 8 schematically illustrates the configuration of the vibrator 90.Referring to FIG. 8, the vibrator 90 includes a reflecting mirror 89 toreflect an incident beam L_(i) and first and second piezoelectricelements 91 a and 91 b to vibrate the reflecting mirror 89. The incidentbeam L_(i) is reflected by the reflecting mirror 89 and emerges as afirst beam L₀₁ when the reflecting mirror 99 does not vibrate or as asecond beam L₀₂ when the reflecting mirror 89 vibrates. The beams L₀₁and L₀₂ emerging from the reflecting mirror 89 are mixed and averagedspatially, thereby significantly reducing or eliminating laser speckle.The vibrator 90 may be reflective or transmissive.

When the vibrator 90 is reflective, as illustrated in FIG. 7, thevibrator 90 also changes a propagation path of the beam emitted from thelaser light source 80, thus contributing to a reduction in the size ofthe projection system. While it is described above that the vibrator 90is disposed between the beam-shaping unit 86 and the display device 92,the vibrator 90 may alternatively be disposed between the optical fiberbundle 82 and the beam-shaping unit 86.

The beam reflected by the vibrator 90 is incident on the display device92 and is spatially modulated according to an input signal to producethe image that is then enlarged and projected onto the screen 96 by theprojection lens unit 94.

Referring to FIG. 7, an illumination system according to anotherembodiment of the present general inventive concept includes the laserlight source 80 having a plurality of lasers to emit laser beams ofdifferent wavelengths, the optical fiber bundle 82 to divide the laserbeam emitted by the laser light source 80 into the sub-beams, thebeam-shaping unit 86 to shape the sub-beams to match the shape of thedisplay device 92 to produce the image, and the vibrator 90 to vibratethe sub-beams shaped by the beam-shaping unit 86 in order to temporallyaverage the sub-beams.

The illumination system according to the embodiment of FIG. 7 uses theoptical fiber bundle 82 to divide the beam emitted from the laser lightsource 80 into the sub-beams and the vibrator 90 to temporally averagethe sub-beams, thereby significantly reducing or eliminating laserspeckle.

The beam-shaping unit 86 may be designed in various configurations.Since the beam-shaping unit 86 performs substantially the sameoperations as the beam-shaping unit 56 of FIG. 2, a description thereofwill be omitted.

The embodiments of the present general inventive concept provide anillumination system that can significantly reduce and eliminate speckleproduced due to coherence of a laser beam and a projection systememploying the same that can provide improved image quality.

The embodiments of the present general inventive concept use a rotatingDOE or a vibrator to temporally or spatially average sub-beams, therebyeffectively removing laser speckle. The embodiments of the presentgeneral inventive concept also use an optical fiber bundle having aplurality of optical fibers with the same length to divide a beamemitted from a laser light source into sub-beams, thus reducingcoherence of the laser beam and laser speckle.

Although a few embodiments of the present general inventive concept havebeen shown and described, it will be appreciated by those skilled in theart that changes may be made in these embodiments without departing fromthe principles and spirit of the general inventive concept, the scope ofwhich is defined in the appended claims and their equivalents.

1. An illumination system to remove speckle of a laser beam, theillumination system comprising: a laser light source having at least onelaser to emit a laser beam; a diffractive optical element to divide thelaser beam emitted from the laser light source into a plurality of firstsub-beams and to periodically move to temporally average the speckle ofthe laser beam; and an optical fiber bundle including a plurality offibers with the same length to divide the first sub-beams into smallersecond sub-beams such that an image is formed according to the smallersecond sub-beams.
 2. The illumination system of claim 1, wherein each ofthe plurality of first sub-beams comprises a plurality of beamlets thatare focused in an overlaying fashion on one another.
 3. The illuminationsystem of claim 1, wherein the diffractive optical element is rotatablewith respect to the laser beam.
 4. The illumination system of claim 1,further comprising: a beam-shaping unit to convert a cross-section ofeach of the second sub-beams into a predetermined shape.
 5. Anillumination system, comprising: a laser light source unit to emit alaser beam; a movable temporal averaging unit to temporally average thelaser beam emitted from the laser light source unit; and an opticalfiber bundle having a plurality of optical fibers each having the samelength to divide the averaged laser beam emitted from the laser lightsource unit into a plurality of sub-beams so that an image is formedaccording to the sub-beams.
 6. The illumination system of claim 5,wherein the movable temporal averaging unit comprises: a diffractiveoptical element to spatially average the laser beam emitted from thelaser light source by dividing the laser beam into a plurality ofoverlapping beams; and a driving unit to periodically move thediffractive optical element to temporally average the laser beam emittedfrom the laser light source.
 7. A projection system to remove speckle ofa laser beam, the projection system comprising: a laser light sourcehaving at least one laser to emit a laser beam; a diffractive opticalelement to divide the laser beam emitted from the laser light sourceinto a plurality of first sub-beams and to periodically move totemporally average the speckle of the laser beam; an optical fiberbundle including a plurality of fibers with the same length to dividethe first sub-beams into smaller second sub-beams; a beam-shaping unitto shape the second sub-beams output by the optical fiber bundle; adisplay device to produce an image using the second sub-beams shaped bythe beam shaping unit; a screen; and a projection lens unit to enlargeand project the image onto the screen.
 8. The projection system of claim7, wherein each of the plurality of first sub-beams comprises aplurality of beamlets that are focused in overlaying fashion on oneanother.
 9. The projection system of claim 7, wherein the diffractiveoptical element is ratable.
 10. The projection system of claim 7,further comprising: a light path changer disposed between thebeam-shaping unit and the display device.